This invention relates to an automatic doffing apparatus for doffing full bobbins formed on winding spindles which are disposed parallel to each other on a yarn; processing machine, such as a draw-twister for synthetic yarn and a melt spinning machine for synthetic yarn, more especially, the present invention relates to an automatic doffing and donning apparatus for replacing full bobbins formed on winding spindles with empty bobbins.
In the modern manufacturing process of synthetic yarn packages, since the weight of individual full bobbins is rapidly increasing so as to increase productivity, manual handling of such a full bobbin becomes troublesome. On the other hand, since the yarn processing speed is increased, the frequency of the replacement of full bobbins with empty bobbins, in other words the doffing and donning operations, is increased. Due to the increases in the weight of individual full bobbins and the frequency of the doffing and donning operations, manual handling of full bobbins becomes very difficult. To obviate the above-mentioned difficulty the requirement for an automatic doffing and donning apparatus is increasing.
Various types of automatic doffing and donning apparatus have been proposed, which can be classified into two types. One is a fixed-type doffing and donning apparatus which is connected to a yarn processing machine and which simultaneously can doff all full bobbins formed on winding spindles of the yarn processing machine. The other is a movable type doffing and donning apparatus which can move in front of a yarn processing apparatus and which can doff a predetermined number of full bobbins from winding spindles of the yarn processing machine.
Since the fixed type doffing and donning apparatus is disposed on each yarn processing machine, the cost of the equipment of the fixed type doffing and donning apparatus may be higher than that of the movable type doffing and donning apparatus when a plurality of yarn processing machines is provided with doffing and donning apparatus. Furthermore, the operating efficiency of the fixed type doffing and donning apparatus is lower than that of the movable type doffing apparatus. In addition, since the fixed type doffing apparatus is permanently mounted on a yarn processing machine and is located in an aisle between two adjacent yarn processing machines, the distance between the adjacent two yarn processing machines must be increased to ensure an operational space for operators. However, in a conventional yarn processing mill, since the width of the aisle, in other words the distance between two adjacent yarn processing machines, has been designed to be narrow so as to allow installation of more machines in a mill, operations performed by operators around the conventional yarn processing machine may be disturbed by the provision of the fixed type doffing and donning apparatus.
Accordingly, the movable type doffing and donning apparatus is superior to the fixed type doffing and donning apparatus. A movable type doffing apparatus is disclosed in Japanese Published Patent Application Sho 50-10970. The disclosed apparatus carries a number of empty bobbins at an upper portion thereof and receives a number of full bobbins which are doffed thereby from a yarn processing machine at a lower portion thereof by means of a doffing means. Thereafter the empty bobbins which are carried thereon are donned on winding spindles of the yarn processing machine. It is necessary for the above-mentioned doffing and donning apparatus to be moved to a predetermined unloading position, which is far from the yarn processing machine, after a predetermined number of full bobbins are doffed so that the full bobbins can be unloaded from the apparatus and empty bobbins can be loaded on the apparatus. A great amount of operating time is consumed in the movement to the unloading position and, as a result, the doffing and donning apparatus is not fully used. Accordingly, although the equipment cost of the doffing and donning apparatus is very high, the operating efficiency of the doffing and donning apparatus is low. In addition, since full bobbins doffed by the doffing apparatus and empty bobbins donned by the doffing apparatus, the sizes of which bobbins are recently increasing, are carried on the doffing and donning apparatus, the size and the weight of the doffing apparatus becomes large. As a result, a wide space for installation of the large doffing and donning apparatus and a strong floor construction for bearing the weighty doffing and donning apparatus are necessary, and the total cost of the mill becomes high. On the other hand, when the doffing and donning apparatus is installed in a conventional yarn processing mill, alteration of the mill for meeting the above-mentioned requirements with regard to the space and the floor construction is necessary. It is also a problem that, since the doffing and donning apparatus moves in accordance with a complex control program, which includes a program for preventing collision between the doffing apparatus, the cost of the control system is high.
Another movable type doffing and donning apparatus is disclosed in Japanese Laid-open Patent Application Sho 51-112935. The disclosed apparatus comprises a first bobbin catching means which dons empty bobbins from reservoir means to winding spindles of a spinning machine and a second bobbin catching means which doffs full bobbins from the winding spindles to the reservoir means.
The first and the second bobbin catching means are moved along separate passages, which have a distance therebetween and are vertically parallel to each other, so that the bobbin catching means do not interfere with each other. This movable type doffing and donning apparatus can obviate the problems of loading and unloading bobbins and the weighty apparatus which are inevitable with the doffing and donning apparatus disclosed in the above-mentioned Japanese Published Patent Application Sho 50-10970. This doffing and donning apparatus has the first bobbin catching means and the second bobbin catching means mounted separately from each other on the doffing apparatus with regard to the winding spindles of the spinning machine (in other words, mounted separately from each other in a transverse direction of the apparatus), so that the passages of the full bobbins and the empty bobbins do not interfere with each other. This doffing and donning apparatus can be utilized for doffing full bobbins from and donning empty bobbins on winding spindles of a particular yarn processing machine, such as a cotton spinning machine, which has a sufficiently wide vertical distance between the winding spindles thereof and the reservoir means. However, this doffing and donning apparatus is difficult to utilize for doffing full bobbins from and donning empty bobbins on winding spindles of a yarn processing machine, such as a draw-twister for synthetic yarn, which has a very small vertical distance, compared with the bobbin length, between the winding spindles thereof and the reservoir means. In addition, when a doffed full bobbin or an empty bobbin to be donned is oscillated, the full bobbin or the empty bobbin may touch another empty bobbin or full bobbin and the yarn wound around the full bobbin which is touched by another bobbin may be damaged. To obviate such yarn damage, it is necessary to increase the above-mentioned distance between the winding spindles and the reservoir means and, as a result, the size of the doffing and donning apparatus is increased. In addition, since it is necessary to provide the first and second passages of the first and second yarn catching means separately from each other along the length of the apparatus, the size of the apparatus is also increased.
In some yarn processing machines, such as a draw-twister of a synthetic yarn, since yarn guides, draw rollers and heaters are located at positions over winding spindles, it is difficult to doff full bobbins from the winding spindles along vertical passages and to don empty bobbins on the winding spindles along vertical passages. In this regard, since the doffing and donning apparatus disclosed in the above-mentioned Japanese Laid-open Patent Application Sho. 51-112935 moves full bobbins and empty bobbins along vertical passages, it can not be utilized for the doffing and donning operation for such yarn processing machines. It should be noted, that it is very difficult to vary the vertical passages to other passages, such as curved passages, in the above-mentioned doffing and donning apparatus.